Solid surface sheets containing post-consumer recycled materials and methods of making same

ABSTRACT

Embodiments of the present invention are directed to solid surface sheets and methods of making solid surface sheets, wherein the method comprises dissolving post-consumer recycled polystyrene in a first liquid resin precursor to form a blend, solidifying the blend via curing, grinding the solidified blend into recycled particles, adding the recycled particles and filler into a second liquid resin precursor to produce a solid surface precursor, and molding and curing the solid surface precursor to produce the solid surface sheet.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 12/957,456 filed Dec. 1, 2010, now U.S. Pat. No. 8,445,552.

BACKGROUND

The present invention generally relates to decorative solid surfacematerials, and specifically relates to decorative solid surface sheetscomprising post-consumer recycled materials, such as recycledpolystyrene, or pre-consumer materials, such as byproducts produced fromthe production of the solid surface material.

SUMMARY

In one embodiment, a method of making solid surface sheets is provided.The method comprises dissolving post-consumer recycled polystyrene in afirst liquid resin precursor to form a blend, solidifying the blend viacuring, grinding the solidified blend into recycled particles, addingthe recycled particles and filler into a second liquid resin precursorto produce a solid surface precursor, and molding and curing the solidsurface precursor to produce the solid surface sheet.

In another embodiment, a solid surface sheet is provided. The solidsurface sheet comprises filler, polyester resin, and recycled particlescomprising a blend of post-consumer recycled polystyrene and polymericresin.

The features and advantages of the present invention will becomeapparent from the following description.

DETAILED DESCRIPTION

Embodiments of the present invention are directed to solid surfacesheets and methods of making solid surface sheets, specifically solidsurface materials that utilize post-consumer recycled material (e.g.,general purpose polystyrene (“GPPS”)). The post-consumer recycledmaterial may be any product discarded by the consumer or end user, forexample, any foamed polystyrene product such as a cup, packing peanuts,or any other product comprising recyclable polystyrene.

The solid surface sheets may also comprise pre-consumer recycledmaterial (dust and small particulates) comprising recycled byproducts ofthe manufacturing process. Typically, these byproduct particles areground and sized before being re-added to the process of making solidsurface sheets; however, it is contemplated that the byproduct particlesmay be directly added back into the process. By incorporating therecycled materials into the solid surface sheets, the solid surfacesheets may receive Leadership in Energy and Environmental Design(“LEED”) credits. The LEED is the internationally recognized greenbuilding certification system.

The solid surface sheets may comprise polymeric resin (e.g., a polyesterresin), and recycled particles comprising a blend of post-consumerrecycled material of polymeric resin. In one embodiment, the blend is ahomogeneous blend. As used herein, “recycled particles” refer to theblend of recycled material and polymeric resin produced in accordancewith the present invention. As will be described below, post-consumerand pre-consumer recycled materials are dissolved in a liquid resinprecursor to produce the recycled particles, and then these recycledparticles are mixed with further polymeric resin as well as anyadditional fillers and additives to produce the solid surface sheets.

In addition to the post-consumer recycled material, the solid surfacesheet may also comprise the pre-consumer recycled particulates asdescribed above. As will be described below, the post-consumer recycledmaterial typically is dissolved before being added into the solidsurface sheet; however, it is not necessary to dissolve the pre-consumerrecycled material before adding into the solid surface sheet.

For the recycled particles, the blend is an insoluble structure producedby the polymerization of the post-consumer recycled material and aliquid resin precursor. Liquid resin precursors, which are used in thedissolution of the pre-consumer recycled material and the post-consumerrecycled material and the polymerization with the recycled materialtherewith, may include various components as long as they can be formedinto a solid surface material by curing as described in the methodsbelow. Preferred free radical, heat curable resins particularly usefulin the practice of the present invention are thermosetting unsaturatedpolyester resins and thermosetting polyacrylate resins, and combinationsthereof. Examples of useful unsaturated polyester resins are reactionproducts of unsaturated dicarboxylic acids, or unsaturated dicarboxylicacids and saturated dicarboxylic acids, with glycols, such as maleicacid, phthalic acid and dipropylene glycol monomers respectively.Examples of useful polyacrylate resins include various kinds ofconventional acrylic group monomers, acrylic group partial polymers,vinyl monomers for copolymerization other than acrylic group monomers,or oligomers. The above reactive monomers are not considered exhaustive;however, the use of methyl methacrylate monomer is preferred. Additionaluseful thermosettable polymers include epoxies, urethanes,acrylo-urethanes, melamines and combinations thereof.

Noting that styrene monomer is a useful monomeric crosslinker, thepresent inventors recognized that the post-consumer recycled material(e.g., general purpose polystyrene (“GPPS”)) could be utilized as acrosslinker. As a result, the present inventors recognized that usingpost-consumer recycled polystyrene is beneficial, as it can be brokendown into styrene monomers that are then used as a crosslinker. While itis contemplated that the polystyrene is fully broken down into styrenemonomer, in specific embodiments, the polystyrene is typically not fullybroken down into styrene monomers. Consequently, utilizing post-consumerrecycled polystyrene is not only environmentally beneficial, but isuseful in the polymerization process that yields the recycled particlesof the solid surface material.

Without being limited to these components, the embodiments of thepresent invention may utilize methyl methyacrylate monomer as the liquidresin precursor used to dissolve the pre-consumer recycled material andthe post-consumer recycled material. After the recycled solid particlesare produced, one or more embodiments of the present invention mayutilize a polyester resin for mixing with the recycled particles in theproduction of the solid surface sheet. The combination of the methylmethyacrylate resin and the polyester resin is beneficial, because thepolyester resin tends to impart toughness to the solid surface sheet andthe methyl methyacrylate resin tends to impart flexibility for theproduced recycled particles.

While the solid surface material can be unfilled, it is preferred insome embodiments to include filler material. Suitable fillers include,for example, aluminum trihydrate, calcium carbonate, titanium dioxide,barium sulfate, magnesium hydroxide, and talc, which as examples, arenot considered to be exhaustive and not intended to limit the scope ofthe claimed invention. In exemplary embodiments, the filler is aluminumtrihydrate.

It is also known to include in solid surface materials other optionaladditives such as polymeric particulates, pearlescent particles,pigments, dyes, flame retardant agents, release agents, fluidizingagents, viscosity control agents, curing agents, antioxidants,toughening agents (e.g., abrasion resistant materials like Sartomer®SR399 dipentaerythritol pentaacrylate oligomer), catalysts, and the likeas is well known to those of ordinary skill in the art. For example,additional pigments having differing or contrasting colors may also beadded to the composition. The inclusion of minor amounts of any or allof these additives is contemplated. Additionally, catalysts, such asmethyl ethyl ketone peroxide (MEKP), and other catalysts may also beadded to the mixture. The catalyst used and the concentration of thecatalyst is matched to the particular polymer or polymers, andprocessing conditions being used.

Various amounts are contemplated for the components of the recycledparticles. The recycled particles may comprise up to about 55% by weightpre-consumer recycled material and post-consumer recycled material, orfrom about 25 to about 45% by weight pre-consumer recycled material andpost-consumer recycled material. The recycled particles may comprisefrom about 20 to about 60% by weight polymeric resin (for example,methyl methacrylate), or from about 25 to about 45% by weight polymericresin. The recycled particles may comprise from about 20% to about 80%by weight filler (e.g., aluminum trihydrate), or from about 30% to about50% by weight filler. The remainder of the recycled particles, forexample, up to about 10% by weight additional additives, such ascatalysts, and pigments.

The solid surface sheets, which incorporate the recycled particles, maycomprise up to about 55%, or up to about 35 to about 50% by weightrecycled particles. Considering that much of the recycled particles arecomprised of polymeric resin, about 20% by weight of the solid surfacematerial is then comprised of pre-consumer and post-consumer recycledmaterial, or about 15 to about 20% by weight of pre-consumer andpost-consumer recycled material. Without being bound by theory,utilizing more than 20% of the pre-consumer and post-consumer recycledmaterial may be detrimental to the fire resistance and strength of thesolid surface material. In further embodiments, the solid surface sheetmay comprise from above 0 to about 10% by weight, or from above 0 toabout 5% by weight of the post-consumer recycled material (e.g.,polystyrene). Additionally, the solid surface sheet may comprise fromabove 0 to about 15% by weight, or from above 10 to about 15% by weightof the pre-consumer recycled material.

The solid surface sheet may also comprise from about 20 to about 30% byweight of polyester resin, or from about 24 to about 28% by weight ofpolyester resin. The filler (e.g., the aluminum trihydrate) may beincluded in both the recycled particles and in the solid surface sheetseparate from the recycled particles. In one embodiment, the solidsurface may comprise from about 40 to about 70% by weight or from 50 toabout 60% by weight aluminum trihydrate, wherein up to about 50% is inthe recycled particles and from about 20 to about 30% of the aluminumtrihydrate is present in the solid surface sheet separate from therecycled particles. The remainder of the solid surface sheet maycomprise, for example, up to about 10% by weight additional additives,such as catalysts, and pigments. In one embodiment, the ratio by weightof aluminum trihydrate and polyester resin to pre-consumer andpost-consumer recycled material is from about 1:5 to 1 to about 1:1.

Turning to the method of producing the solid surface sheet, the methodof making the solid surface sheets comprises the steps of dissolvingpost-consumer recycled material in a liquid polymeric resin precursor(e.g., methyl methacrylate) to form a blend, solidifying the blendcomprising the post-consumer recycled material via curing, grinding thesolidified blend into recycled particles, and mixing the recycledparticles and filler with a polyester resin to produce a solid surfacesheet.

In one exemplary embodiment for the production of the recycledparticles, post-consumer recycled material (e.g., GPPS) and pre-consumerfines are added to a liquid polymeric resin precursor (methylmethacrylate (“MMA”) oligomer) in a suitable mixing vessel and agitateduntil fully dissolved into a blend having a syrup consistency. The“syrup” commonly refers to the uncured liquid state of a polymer, wheresaid polymer is present in solution with a suitable crosslinkingmonomer. Any suitable mixing method may be used, including adispersing-type blade mixer, kneading mixer, screw mixer, or doubleplanetary mixer. At which point, additional additives and fillers suchas aluminum trihydrate, Sartomer® SR399 oligomer, pigments, cobalt andmore MMA may be added to the GPPS-MMA syrup and blended to a thin pastewith a viscosity of approximately 60 kCPS. A catalyst (e.g., a methylethyl ketone peroxide (MEKP)) catalyst may then be added to the mixture.

The mixture is dispensed from the mixing vessel and cast into a suitableopen mold which is sized to provide a sheet of solid surface materialhaving the desired length, width, and thickness dimensions. In specificembodiment, the mixture present in the mold may be incorporated into avacuum chamber sized to be able to completely contain the mold, so thatthe molded mixture may be cured under vacuum pressure to produce a hardgelled structure. In an exemplary embodiment, the molded mixture isplaced under 24 inches Hg vacuum pressure and hard-gelled at a curingtemperature of about 150 to 170° F.

Once the blend of pre-consumer and post-consumer recycled materials havesolidified, it is de-molded and placed in a “post-cure” oven to completethe polymerization and curing process. For example, the sheet may bedemolded, and post-cured. Post-curing is typically carried out attemperatures of from about 150 to about 200° F. for a period of fromabout 1 to about 4 hours, depending on the size, thickness, andcomposition. In a preferred embodiment, post curing is conducted at 190°F. Preferably, heating of the post-cure oven is accomplished byre-circulation of hot air over the curing material. Optionally, coolingmay be conducted, typically by gradually reducing the temperature ofthat recirculating oven air. In one exemplary embodiment, cooling occursat a rate of approximately 1° F. per minute, such that the solidifiedmixture is cooled down to at least 115° F. (46° C.) before removal fromthe oven. To produce the recycled particles, the solidified homogenousblend comprising pre-consumer and post-consumer recycled material isthen ground via milling, grinding, or any other suitable technique toproduce the recycled particles.

Upon production of the recycled particles, the recycled particles arethen added to a polyester resin with filler (e.g., aluminum trihydrate),and optional ingredients such as polymeric resin (e.g., MMA), pigments,and catalysts (e.g., MEKP catalyst). Like the production of the recycledparticles, the mixture is poured into molds and cured in a vacuumchamber to produce a hard-gelled solid surface precursor. The solidsurface precursor is then demolded, and post-cured, for example, at 175°F. for 3 hours. The resulting solid surface sheets may then be sanded,polished, and stacked for storage. Accordingly, the final product is asolid surface material with particles that contain post-consumerrecycled material (polystyrene) and pre-consumer recycled fines.

It is further noted that terms like “preferably,” “generally”,“commonly,” and “typically” are not utilized herein to limit the scopeof the claimed invention or to imply that certain features are critical,essential, or even important to the structure or function of the claimedinvention. Rather, these terms are merely intended to highlightalternative or additional features that may or may not be utilized in aparticular embodiment of the present invention.

For the purposes of describing and defining the present invention it isadditionally noted that the term “substantially” is utilized herein torepresent the inherent degree of uncertainty that may be attributed toany quantitative comparison, value, measurement, or otherrepresentation. The term “substantially” is also utilized herein torepresent the degree by which a quantitative representation may varyfrom a stated reference without resulting in a change in the basicfunction of the subject matter at issue.

Having described the invention in detail and by reference to specificembodiments thereof, it will be apparent that modifications andvariations are possible without departing from the scope of theinvention defined in the appended claims. More specifically, althoughsome aspects of the present invention are identified herein as preferredor particularly advantageous, it is contemplated that the presentinvention is not necessarily limited to these preferred aspects of theinvention.

What is claimed is:
 1. A method of making solid surface sheetscomprising: dissolving a post-consumer recycled polystyrene in a firstliquid resin precursor to form a blend; solidifying the blend viacuring; grinding the solidified blend into recycled particles; addingthe recycled particles and a filler into a second liquid resin precursorto produce a solid surface precursor; and molding and curing the solidsurface precursor to produce the solid surface sheets.
 2. The method ofclaim 1 wherein the filler comprises aluminum trihydrate.
 3. The methodof claim 1 further comprising hard gelling the solid surface precursor.4. The method of claim 1 wherein the blend is a homogeneous blend. 5.The method of claim 4 wherein the homogeneous blend defines an insolublestructure produced by polymerization of the post-consumer recycledpolystyrene and the first liquid resin precursor.
 6. The method of claim1 wherein the first liquid resin precursor comprises methyl methacrylateoligomer.
 7. The method of claim 1 wherein the second liquid resinprecursor comprises polyester resin.
 8. The method of claim 1 furthercomprising adding pre-consumer byproduct particulates to the blend.
 9. Amethod of making a solid surface sheet comprising: dissolving apost-consumer recycled polystyrene in a first liquid resin precursorselected from the group consisting of acrylic group monomers andoligomers, wherein the post-consumer recycled polystyrene breaks down toa styrene monomer crosslinker upon dissolution in the first liquid resinprecursor to form a blend; solidifying the blend via curing; grindingthe solidified blend into a crosslinked, polymerized blend of recycledparticles; adding the crosslinked, polymerized blend of recycledparticles and a filler into a polyester resin to produce a solid surfaceprecursor; and molding and curing the solid surface precursor to producethe solid surface sheet.
 10. The method of claim 9 wherein the blend isa homogeneous blend.
 11. The method of claim 10 wherein the homogeneousblend defines an insoluble structure produced by polymerization of thepost-consumer recycled polystyrene and the first liquid resin precursor.12. The method of claim 9 wherein the first liquid resin precursorcomprises methyl methyacrylate oligomer.
 13. The method of claim 9wherein the filler is aluminum trihydrate.
 14. The method of claim 9wherein the crosslinked, polymerized blend of recycled particles furthercomprises pre-consumer recycled particulates.
 15. The method of claim 14wherein the ratio by weight of the filler and the polyester resin to thepre-consumer recycled particulates and the post-consumer recycledpolystyrene is from about 1:5 to about 1:1.
 16. The method of claim 14wherein the solid surface sheet comprises about 15 to about 20% byweight in total of the pre-consumer recycled particulates and thepost-consumer recycled polystyrene.
 17. The method of claim 9 whereinthe crosslinked, polymerized blend of recycled particles comprise about45 to about 55% of the post-consumer recycled polystyrene and the firstliquid resin precursor.
 18. The method of claim 9 wherein thecrosslinked, polymerized blend of recycled particles further comprisesaluminum trihydrate.
 19. The method of claim 9 wherein the solid surfacesheet comprises from about 20 to about 30% by weight of the polyesterresin.
 20. A method of making a solid surface sheet comprising:dissolving a post-consumer recycled polystyrene in a first liquid resinprecursor, the first liquid resin precursor comprises methylmethyacrylate oligomer, wherein the post-consumer recycled polystyrenebreaks down to a styrene monomer crosslinker upon dissolution in thefirst liquid resin precursor to form a blend; solidifying the blend viacuring; grinding the solidified blend into a crosslinked, polymerizedhomogeneous blend of recycled particles; adding the crosslinked,polymerized homogeneous blend of recycled particles and a fillercomprising aluminum trihydrate into a polyester resin to produce a solidsurface precursor; and molding and curing the solid surface precursor toproduce the solid surface sheet.